Wednesday, October 05, 2011

Birth Order and the Big Five

A new study reports that there is no connection between birth order and Big 5 personality traits:
The hypotheses of Sulloway (1996) regarding birth order differences in five-factor model personality traits were tested in a sample of 231 college students with the NEO Five-Factor Inventory (NEO-FFI; Costa & McCrae, 1992). Data were collected from three sources (self, peer, and parent) to systematically evaluate previous observations that birth order differences are more commonly found when ratings are obtained from family members than from observers outside the family (Ernst & Angst, 1983). Using a between-family design, students were selected only from families with two or three full biological siblings and no half-siblings, step-siblings, or adopted siblings. Firstborn (n = 103) and laterborn (n = 128) students were compared using NEO-FFI ratings by the self, by a same-sex college peer, and by a biological parent. No birth order differences were found for any of the five NEO-FFI scores using any of the three rating sources. Effect sizes (Cohen’s d) were less than .20 for all comparisons.


  1. Personality traits have complicated relationships with each other, so I'm skeptical that we should be studying correlations for the traits themselves, rather than the 32 personalities predicted by the Big 5 indicator.

    I'll admit ignorance of the math needed to shore up this observation, so a grain of salt would be apropos.

  2. This is how Frank Sulloway conducts 'science':

  3. Sure would be nice to check my thoughts against the study without paying $30. No science for proles, I guess.

  4. Anonymous2:58 PM


    Mildly off-topic:

    Recently you showed a study on ethnic differences on narcissism.

    Narcissism is probably just another psychological trait other than the big five, right? What are other quantitative psychological traits that are important also?

    Mostly it's about IQ and the big five, but there must be lots and lots more out there. As an amateur it's hard for me to judge for myself, please elaborate.


  5. Birth order stuff doesn't seem to have panned out.

  6. Anonymous4:20 PM

    Judith Rich Harris has done some good analysis on the birth order effect. You can see some of her essays here:

    I believe that she criticised some of the previous research on birth order and personalities for not taking into account family size; members of small families achieve more and also have more first-borns. Another source of error is using within-family ratings of personality traits which are more age dependant and differ from outside observer ratings.

    Apparently she had some trouble obtaining a Ph.D, possibly due to her challenging of various dogmas about environmental influence but now she is fairly well respected.


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